Disk-based storage devices such as hard disk drives (HDDs) are used to provide non-volatile data storage in a wide variety of different types of data processing systems. A typical HDD comprises a spindle which holds one or more flat circular storage disks, also referred to as platters. Each storage disk comprises a substrate made from a non-magnetic material, such as aluminum or glass, which is coated with one or more thin layers of magnetic material. In operation, data is read from and written to tracks of the storage disk via a read/write head that is moved precisely across the disk surface by a positioning arm as the disk spins at high speed.
HDDs often include a system-on-chip (SOC) to process data from a computer or other processing device into a suitable form to be written to the storage disk, and to transform signal waveforms read back from the storage disk into data for delivery to the computer. The HDD includes a preamplifier that interfaces the SOC to the read/write head used to read data from and write data to the storage disk. The SOC communicates with the preamplifier through a digital interface in order to program preamplifier parameters such as signal gain and bandwidth, and to receive back information such as system faults detected by the preamplifier.
The SOC has extensive digital circuitry and has typically used advanced CMOS technologies to meet cost and performance objectives. This has driven the SOC to use power supply voltages different than those used by the preamplifier and has over time resulted in the digital interface between the SOC and preamplifier using a variety of different logic high input signal levels, such as 3.3V, 2.5V or 1.8V logic levels. The preamplifier is also used in factory servo writers that format the storage disk, and some of the servo writers use 5V logic levels to communicate with the preamplifier.